This work is concerned with establishing Tetrahymena as a primary research instrument for the investigation of basic eukaryotic mechanism. Of particular interest are cytogenetic studies leading to mutational dissection of cellular processes and comparative studies directed to an understanding of the relationship among the ciliates and their relations to other eukaryotes. Particular projects are concerned with mating type determination, functional inertia, structural inertia, the measurement of time and the design of senescence.